Day 9 September 25th Chapter 6

Dr Amy B HollingsworthThe University of Akron

On My To-Do List

1. Grade Homework from Sept 19th (me)2. Post Homework opportunity on Springboard

(me) – will be due Sunday at 11:303. Post last lecture recording (I was in hospital)4. Answer student emails5. Input Interim Reports

Continuity and varietyLectures by Mark Manteuffel, St. Louis Community

College

Chapter 6: Chromosomes and Cell Division

Insert new photo (Jackson 5)

There are different

types of cell

division.

Mitosis and Meiosis

6.1 Immortal cells can spell trouble: cell division in sickness and health.

Telomeres The telomere is

like a protective cap at the end of the DNA.

Every time a cell divides, the telomere gets a bit shorter.

Insert new fig 6-1

Progeria – rarely live past 13

“Cancer cells are those which have forgotten how to

die.”—Harold Pinter

6.2 Some chromosomes are circular, others are linear.

6.3 Prokaryotes divide by binary fission.

6.5 Cell division is preceded by replication.

Persistence and propagation

Replication

The process of DNA duplication

Complementarity

The characteristic that in the double-stranded DNA molecule the base on one strand always has the same pairing-partner (called the complementary base) on the other strand

Every “A” (adenine) pairs with “T” (thymine) and vice-versa.

Every “G” (guanine) pairs with “C” (cytosine) and vice-versa.

Errors sometime occur when DNA duplicates

itself.

Why might that be a good thing?

Mutation

A variety of errors can occur during replication.

Several DNA repair processes occur after replication.

If an error remains, however, the sequences in a replicated DNA molecule (including the genes) can be different from those in the parent molecule.

6.6 Most cells are not immortal: Mitosis generates replacements.

What is dust?

Why is it your fault?

Mitosis has just one purpose:

To enable cells to generate new, genetically identical cells.

There are two different reasons for this need:1. Growth2. Replacement

Apoptosis

The pre-planned process of cell suicide

Certain cells are targeted for apoptosis.

Mitosis

The number of (somatic) cells that must be replaced by mitosis every day is huge.

The rate at which mitosis occurs varies dramatically.

Mitosis leads to duplicate cells.

Parent cells daughter cells

6.8 The Details

Mitosis is a four-step process.

Preparation for Mitosis: The

Chromosomes Replicate

Animal chromosomes are linear.

So why do they look like the letter “X” in pictures?

Sister Chromatids

A chromosome and its identical replicated copy, joined at the centromere.

6.9 Cell division out of control means cancer.

Cancer

Unrestrained cell growth and division…

…can lead to tumors…

…the second leading cause of death in the United States! (20%, leading is heart disease)

Tumor Growth

Cancer cells have several features that distinguish them from normal cells, including…

Benign and Malignant Tumors

What is cancer?

How does it usually cause death?

Why is the treatment for cancer often considered as bad as the disease?

Cancer is unrestrained cell growth and division.

Cancer can lead to large masses of cells called malignant tumors that can cause serious health problems.

Treatment focuses on killing or slowing the division of the cells using chemotherapy and/or radiation.